Engine Modes
Pressure includes five compression voices built around distinct response topologies. The Mode selector switches the entire compression algorithm - not just a filter or saturation flavor, but the fundamental gain reduction behavior.
MIX - VCA
Clean bus glue characterThe VCA engine is Pressure's cleanest glue voice. It's punchy, versatile, and a strong default choice for mix bus and group compression.
Ratio range: 2:1 to 8:1 (PRESSURE driven)
Attack: 0.1-100 ms (clamped). Scales from 30 ms at P=0 to 1 ms at P=1.0.
Release: 10-2000 ms (clamped). From 1200 ms at P=0 to 100 ms at P=1.0.
Knee: Scales inversely with ratio - wide (12 dB) at low PRESSURE, narrow (3 dB) at high. The result is gentle control at low settings and firmer shaping as you lean on it.
Sidechain HPF:Controlled by TONE. tone² × 60 Hz, range 20-120 Hz (reduced from 150/300 in v1.2 to keep bass in detection per Pro-C 2 Bus defaults).
When to use MIX
- • Stereo bus / mix bus glue
- • Group buses (drums, vocals, strings)
- • Gentle cohesion on submixes
- • Parallel compression blends
INST - FET
Fast, assertive characterThe FET engine is the fastest, most assertive voice in Pressure. At high PRESSURE values, it enters an extreme ratio mode for intentionally colorful control.
Ratio steps:4:1 (P<60%), 8:1 (P<80%), 12:1 (P<92%), 20:1 (P<97%), All Buttons In / 21:1 (P≥97%)
Attack:20-800 μs (microseconds, not milliseconds). This is the fastest attack envelope in Pressure.
Release:50-1100 ms. Follows a V-shaped curve: shortest at P=0 and P=1.0, longest at P=0.5. Formula: 50 + 400 × P × (1-P) ms.
Input drive: Threshold maps to inverted input gain so higher PRESSURE pushes more level into the detector. More drive means more compression and more attitude.
Saturation: Two-stage FET saturation adds harmonic content. Output gain automatically compensates for input drive and saturation gain.
Sidechain HPF: None. The FET engine does not use sidechain filtering.
When to use INST
- • Electric and acoustic guitar
- • Bass guitar (drive and sustain)
- • Synths and keyboards
- • Aggressive vocal compression
- • All Buttons In mode for extreme parallel effects
VOCALS - Opto
Smooth optical characterThe Opto engine uses a smooth, optical-style response. It has no fixed ratio - compression increases naturally with signal level, creating musical dynamics control.
Ratio:Continuously variable from 2:1 to 12:1. Not stepped - the detector's sensitivity creates an emergent ratio that varies with signal level.
Peak Reduction: Maps from PRESSURE via threshold. At P=0.5, peak reduction is ~30 (moderate); at P=1.0, it reaches 60 (heavy).
Attack/Release: Hardwired in the optical cell model - not user-adjustable. The optical element has inherently smooth, program-dependent timing.
Tube warmth:Subtle 2nd harmonic content scaled by sensitivity: 0.038 + sensitivity × 0.013.
TONE behavior:Controls emphasis (not sidechain HPF). Maps directly to the optical cell's emphasis parameter.
When to use VOCALS
- • Lead and backing vocals
- • Voiceover and dialogue
- • Podcast and streaming voice
- • Any source needing transparent, smooth leveling
DRUMS - Dynamics
Direct, hard-knee characterThe Dynamics engine is direct and precise - it controls dynamics without adding much color. Its defining characteristic is a permanently hard knee (0 dB).
Ratio range: 2:1 to 8:1
Attack: 3-30 ms. Slightly slower than VCA to preserve drum transients.
Release: 100-300 ms. Auto-release tuning set separately for program-dependent recovery.
Knee: Always hard (0 dB). No soft-knee option.
Sidechain HPF:Controlled by TONE. tone² × 120 Hz, range 20-120 Hz. Protects kick drum from triggering excessive compression.
When to use DRUMS
- • Individual drum tracks (snare, kick, toms)
- • Drum bus and room mics
- • Percussion and programmed beats
- • Any source where transient preservation is critical
MASTER - VariMu
Wide-knee mastering characterThe VariMu engine is Pressure's widest, slowest voice for gentle mix control. Its always-wide knee and slower release times make compression nearly invisible while adding warmth and cohesion.
Ratio range: 2:1 to 8:1. Variable-mu ratio modulation in the engine makes effective ratio change with signal level.
Attack: Clamped 0.2-30 ms. Lower PRESSURE stays quicker; higher PRESSURE expands into slower mastering-style timing.
Release: 300-5000 ms. This is the longest release range in Pressure and is tuned for broad, low-drama control.
Knee: Always wide (10-24 dB, enforced minimum 10 dB).
Tube warmth:Even harmonics for perceived loudness without actual gain. Formula: 0.23 + tone × 0.32.
Sidechain HPF:Controlled by TONE. tone² × 80 Hz, range 20-160 Hz (reduced from 120/250 in v1.2 to keep the detector more mid-inclusive).
When to use MASTER
- • Master bus sweetening
- • Stereo mix glue (mastering context)
- • Orchestral and cinematic material
- • Any source where warmth and transparency matter
Engine Comparison
VCA
- Max Ratio
- 8:1
- Fastest Attack
- 1 ms
- Knee
- Variable
- SC HPF
- Yes
- Coloration
- Clean
FET
- Max Ratio
- 21:1
- Fastest Attack
- 20 μs
- Knee
- 6 dB fixed
- SC HPF
- No
- Coloration
- Colorful
Opto
- Max Ratio
- 12:1
- Fastest Attack
- Fixed
- Knee
- N/A
- SC HPF
- No
- Coloration
- Warm
Dynamics
- Max Ratio
- 8:1
- Fastest Attack
- 3 ms
- Knee
- Hard (0 dB)
- SC HPF
- Yes
- Coloration
- Transparent
VariMu
- Max Ratio
- 8:1
- Fastest Attack
- 0.2 ms
- Knee
- Wide (10-24 dB)
- SC HPF
- Yes
- Coloration
- Warm
| Engine | Max Ratio | Fastest Attack | Knee | SC HPF | Coloration |
|---|---|---|---|---|---|
| VCA | 8:1 | 1 ms | Variable | Yes | Clean |
| FET | 21:1 | 20 μs | 6 dB fixed | No | Colorful |
| Opto | 12:1 | Fixed | N/A | No | Warm |
| Dynamics | 8:1 | 3 ms | Hard (0 dB) | Yes | Transparent |
| VariMu | 8:1 | 0.2 ms | Wide (10-24 dB) | Yes | Warm |
Swipe sideways to compare
For exact PRESSURE curve values at P=0, P=0.5, and P=1.0, see PRESSURE Control.